The present invention relates to the field of power electronics, and more specifically to power supplies providing temporary electrical power to maintain uninterrupted electrical power to a load during momentary electrical power interruptions.
Many types of electrical systems, especially those on board ships of the U.S. Navy, require an uninterrupted electrical power supply. Continuity of electrical power can be critical to a ship's survival in a war-time situation. Power interruptions to critical shipboard loads may cause a loss of information which can result in degradation of offensive and defensive capabilities. Examples of shipboard systems especially vulnerable to intermittent power losses include computer, navigation, communication, and weapon guidance systems, i.e., virtually all digital electronic systems. Often, power restart can require a substantial period of time.
Battery powered uninterruptible power supplies may be used for long term power interruptions having durations which may vary from minutes to hours. However, these types of power supplies are not practical for momentary power interruptions (milliseconds) for applications requiring relatively large amounts of power, which may be on the order of 10 kw. A battery has a relatively large internal resistance which causes battery output voltage to drop substantially when a large current of short duration is drawn. Thus, many batteries may be required to be connected in parallel in order to instantaneously provide energy at the proper voltage level while avoiding the internal resistance problem. However, this results in a bulky system. Power supplies sometimes have extra output capacitance for energy storage, but generally can not store sufficient energy at their output voltage levels, which may be as low as 5 volts dc, typical of many digital applications. Therefore, there is a need for a physically compact DC electrical power supply which can instantaneously provide up to tens of kilowatts of electrical power for at least 100 ms in the event of power interruptions.